1. Field of the Invention
The present invention relates to a copying machine for forming an image or images selectively on one or both sides of a copying paper and, more specifically, to such a copying machine capable of discharging a copying paper and/or marking paper without forming any image thereon.
2. Description of Related Art
Some copying machine rental system charges rental corresponding to the number of sides of copying papers on which images are formed, and the rental is calculated on the basis of a count indicated on a counter. A conventional copying machine for such a copying machine rental system has a marking paper inserting function for inserting a marking paper between successive copying papers discharged after copying to divide the copying papers into groups, and a reserved copying paper discharging function for discharging papers stored temporarily in an intermediate storage unit and each carrying an image on one side thereof. A counter is incorporated in such a copying machine.
To classify printed copying papers, the marking paper inserting function is applied to inserting a marking paper, such as a colored paper, between the printed copying papers, while the reserved copying paper discharging function is applied to discharging copying papers printed only on one side and temporarily stored in the intermediate storage unit without printing on the other side. The counter counts both the printed copying papers and the marking papers indiscriminately. Accordingly, in some cases, the count of the counter is greater than the number of actually printed sides of copying papers, and hence the rental is greater than normal.
The same problem arises in a duplex copying machine in recording the number of printed copying papers by means of a key counter for individual copying tasks. That is, when some copying papers are left in the intermediate storage unit in the preceding copying task and these copying papers are discharged at the beginning of the next copying task, the number of those copying papers stored in the intermediate storage unit in the preceding copying task which is to be included in the number of printed copying papers of the preceding copying task is added to the number of printed copying papers produced in the subsequent copying task.